[ffigen] Blocking blocks (#1796)

dart-lang · Jan 6, 2025 · 4ebaea4 · 4ebaea4
1 parent 1deeac7
commit 4ebaea4
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Showing 19 changed files with 1,106 additions and 126 deletions.
diff --git a/pkgs/ffigen/CHANGELOG.md b/pkgs/ffigen/CHANGELOG.md
@@ -3,6 +3,7 @@
 - Ensure that required symbols are available to FFI even when the final binary
   is linked with `-dead_strip`.
 - Handle dart typedefs in import/export of symbol files.
+- Add support for blocking ObjC blocks that can be invoked from any thread.
 
 ## 16.0.0
 

diff --git a/pkgs/ffigen/lib/src/code_generator/objc_block.dart b/pkgs/ffigen/lib/src/code_generator/objc_block.dart
diff --git a/pkgs/ffigen/lib/src/code_generator/objc_built_in_functions.dart b/pkgs/ffigen/lib/src/code_generator/objc_built_in_functions.dart
@@ -33,6 +33,8 @@ class ObjCBuiltInFunctions {
       ObjCImport('getProtocolMethodSignature');
   static const getProtocol = ObjCImport('getProtocol');
   static const objectRelease = ObjCImport('objectRelease');
+  static const signalWaiter = ObjCImport('signalWaiter');
+  static const wrapBlockingBlock = ObjCImport('wrapBlockingBlock');
   static const objectBase = ObjCImport('ObjCObjectBase');
   static const blockType = ObjCImport('ObjCBlock');
   static const consumedType = ObjCImport('Consumed');
@@ -207,28 +209,51 @@ class ObjCBuiltInFunctions {
           Parameter(type: _methodSigType(p.type), objCConsumed: p.objCConsumed))
       .toList();
 
-  final _blockTrampolines = <String, ObjCListenerBlockTrampoline>{};
-  ObjCListenerBlockTrampoline? getListenerBlockTrampoline(ObjCBlock block) {
+  final _blockTrampolines = <String, ObjCBlockWrapperFuncs>{};
+  ObjCBlockWrapperFuncs? getBlockTrampolines(ObjCBlock block) {
     final id = _methodSigId(block.returnType, block.params);
     final idHash = fnvHash32(id).toRadixString(36);
-
-    return _blockTrampolines[id] ??= ObjCListenerBlockTrampoline(Func(
-      name: '_${wrapperName}_wrapListenerBlock_$idHash',
-      returnType: PointerType(objCBlockType),
-      parameters: [
-        Parameter(
-            name: 'block',
-            type: PointerType(objCBlockType),
-            objCConsumed: false)
-      ],
-      objCReturnsRetained: true,
-      isLeaf: true,
-      isInternal: true,
-      useNameForLookup: true,
-      ffiNativeConfig: const FfiNativeConfig(enabled: true),
-    ));
+    return _blockTrampolines[id] ??= ObjCBlockWrapperFuncs(
+      _blockTrampolineFunc('_${wrapperName}_wrapListenerBlock_$idHash'),
+      _blockTrampolineFunc('_${wrapperName}_wrapBlockingBlock_$idHash',
+          blocking: true),
+    );
   }
 
+  Func _blockTrampolineFunc(String name, {bool blocking = false}) => Func(
+        name: name,
+        returnType: PointerType(objCBlockType),
+        parameters: [
+          Parameter(
+              name: 'block',
+              type: PointerType(objCBlockType),
+              objCConsumed: false),
+          if (blocking) ...[
+            Parameter(
+                name: 'listnerBlock',
+                type: PointerType(objCBlockType),
+                objCConsumed: false),
+            Parameter(
+                name: 'newWaiter',
+                type: PointerType(NativeFunc(FunctionType(
+                    returnType: PointerType(voidType), parameters: []))),
+                objCConsumed: false),
+            Parameter(
+                name: 'awaitWaiter',
+                type: PointerType(
+                    NativeFunc(FunctionType(returnType: voidType, parameters: [
+                  Parameter(type: PointerType(voidType), objCConsumed: false),
+                ]))),
+                objCConsumed: false),
+          ],
+        ],
+        objCReturnsRetained: true,
+        isLeaf: true,
+        isInternal: true,
+        useNameForLookup: true,
+        ffiNativeConfig: const FfiNativeConfig(enabled: true),
+      );
+
   static bool isInstanceType(Type type) {
     if (type is ObjCInstanceType) return true;
     final baseType = type.typealiasType;
@@ -237,15 +262,18 @@ class ObjCBuiltInFunctions {
 }
 
 /// A native trampoline function for a listener block.
-class ObjCListenerBlockTrampoline extends AstNode {
-  final Func func;
+class ObjCBlockWrapperFuncs extends AstNode {
+  final Func listenerWrapper;
+  final Func blockingWrapper;
   bool objCBindingsGenerated = false;
-  ObjCListenerBlockTrampoline(this.func);
+
+  ObjCBlockWrapperFuncs(this.listenerWrapper, this.blockingWrapper);
 
   @override
   void visitChildren(Visitor visitor) {
     super.visitChildren(visitor);
-    visitor.visit(func);
+    visitor.visit(listenerWrapper);
+    visitor.visit(blockingWrapper);
   }
 }
 

diff --git a/pkgs/ffigen/lib/src/code_generator/writer.dart b/pkgs/ffigen/lib/src/code_generator/writer.dart
@@ -432,6 +432,7 @@ class Writer {
     final s = StringBuffer();
     s.write('''
 #include <stdint.h>
+#import <Foundation/Foundation.h>
 ''');
 
     for (final entryPoint in nativeEntryPoints) {

diff --git a/pkgs/ffigen/pubspec.yaml b/pkgs/ffigen/pubspec.yaml
@@ -41,7 +41,7 @@ dev_dependencies:
   dart_flutter_team_lints: ^2.0.0
   json_schema: ^5.1.1
   leak_tracker: ^10.0.7
-  objective_c: ^4.0.0
+  objective_c: ^4.1.0
   test: ^1.16.2
 
 dependency_overrides:

diff --git a/pkgs/ffigen/test/native_objc_test/block_test.dart b/pkgs/ffigen/test/native_objc_test/block_test.dart
@@ -37,6 +37,8 @@ typedef StructListenerBlock = ObjCBlock_ffiVoid_Vec2_Vec4_NSObject;
 typedef NSStringListenerBlock = ObjCBlock_ffiVoid_NSString;
 typedef NoTrampolineListenerBlock = ObjCBlock_ffiVoid_Int32_Vec4_ffiChar;
 typedef BlockBlock = ObjCBlock_IntBlock_IntBlock;
+typedef IntPtrBlock = ObjCBlock_ffiVoid_Int32;
+typedef ResultBlock = ObjCBlock_ffiVoid_Int321;
 
 void main() {
   late final BlockTestObjCLibrary lib;
@@ -113,6 +115,70 @@ void main() {
       expect(value, 123);
     });
 
+    void waitSync(Duration d) {
+      final t = Stopwatch();
+      t.start();
+      while (t.elapsed < d) {
+        // Waiting...
+      }
+    }
+
+    test('Blocking block same thread', () {
+      int value = 0;
+      final block = VoidBlock.blocking(() {
+        waitSync(Duration(milliseconds: 100));
+        value = 123;
+      });
+      BlockTester.callOnSameThread_(block);
+      expect(value, 123);
+    });
+
+    test('Blocking block new thread', () async {
+      final block = IntPtrBlock.blocking((Pointer<Int32> result) {
+        waitSync(Duration(milliseconds: 100));
+        result.value = 123456;
+      });
+      final resultCompleter = Completer<int>();
+      final resultBlock = ResultBlock.listener((int result) {
+        resultCompleter.complete(result);
+      });
+      BlockTester.blockingBlockTest_resultBlock_(block, resultBlock);
+      expect(await resultCompleter.future, 123456);
+    });
+
+    test('Blocking block same thread throws', () {
+      int value = 0;
+      final block = VoidBlock.blocking(() {
+        value = 123;
+        throw "Hello";
+      });
+      BlockTester.callOnSameThread_(block);
+      expect(value, 123);
+    });
+
+    test('Blocking block new thread throws', () async {
+      final block = IntPtrBlock.blocking((Pointer<Int32> result) {
+        result.value = 123456;
+        throw "Hello";
+      });
+      final resultCompleter = Completer<int>();
+      final resultBlock = ResultBlock.listener((int result) {
+        resultCompleter.complete(result);
+      });
+      BlockTester.blockingBlockTest_resultBlock_(block, resultBlock);
+      expect(await resultCompleter.future, 123456);
+    });
+
+    test('Blocking block manual invocation', () {
+      int value = 0;
+      final block = VoidBlock.blocking(() {
+        waitSync(Duration(milliseconds: 100));
+        value = 123;
+      });
+      block();
+      expect(value, 123);
+    });
+
     test('Float block', () {
       final block = FloatBlock.fromFunction((double x) {
         return x + 4.56;
@@ -664,6 +730,68 @@ void main() {
       expect(blockRetainCount(blockBlock), 0);
     }, skip: !canDoGC);
 
+    test('Blocking block ref counting same thread', () async {
+      DummyObject? dummyObject = DummyObject.new1();
+      DartObjectListenerBlock? block =
+          ObjectListenerBlock.blocking((DummyObject obj) {
+        // Object passed as argument.
+        expect(objectRetainCount(obj.ref.pointer), greaterThan(0));
+
+        // Object bound in block's lambda.
+        expect(dummyObject, isNotNull);
+      });
+
+      final tester = BlockTester.newFromListener_(block);
+      final rawBlock = block!.ref.pointer;
+      expect(blockRetainCount(rawBlock), 2);
+
+      final rawDummyObject = dummyObject!.ref.pointer;
+      expect(objectRetainCount(rawDummyObject), 1);
+
+      dummyObject = null;
+      block = null;
+      tester.invokeAndReleaseListener_(null);
+      doGC();
+      await Future<void>.delayed(Duration.zero); // Let dispose message arrive.
+      doGC();
+
+      expect(blockRetainCount(rawBlock), 0);
+      expect(objectRetainCount(rawDummyObject), 0);
+    }, skip: !canDoGC);
+
+    test('Blocking block ref counting new thread', () async {
+      final completer = Completer<void>();
+      DummyObject? dummyObject = DummyObject.new1();
+      DartObjectListenerBlock? block =
+          ObjectListenerBlock.blocking((DummyObject obj) {
+        // Object passed as argument.
+        expect(objectRetainCount(obj.ref.pointer), greaterThan(0));
+
+        // Object bound in block's lambda.
+        expect(dummyObject, isNotNull);
+
+        completer.complete();
+      });
+
+      final tester = BlockTester.newFromListener_(block);
+      final rawBlock = block!.ref.pointer;
+      expect(blockRetainCount(rawBlock), 2);
+
+      final rawDummyObject = dummyObject!.ref.pointer;
+      expect(objectRetainCount(rawDummyObject), 1);
+
+      tester.invokeAndReleaseListenerOnNewThread();
+      await completer.future;
+      dummyObject = null;
+      block = null;
+      doGC();
+      await Future<void>.delayed(Duration.zero); // Let dispose message arrive.
+      doGC();
+
+      expect(blockRetainCount(rawBlock), 0);
+      expect(objectRetainCount(rawDummyObject), 0);
+    }, skip: !canDoGC);
+
     test('Block fields have sensible values', () {
       final block = IntBlock.fromFunction(makeAdder(4000));
       final blockPtr = block.ref.pointer;

diff --git a/pkgs/ffigen/test/native_objc_test/block_test.h b/pkgs/ffigen/test/native_objc_test/block_test.h
@@ -46,6 +46,8 @@ typedef void (^NullableListenerBlock)(DummyObject* _Nullable);
 typedef void (^StructListenerBlock)(struct Vec2, Vec4, NSObject*);
 typedef void (^NSStringListenerBlock)(NSString*);
 typedef void (^NoTrampolineListenerBlock)(int32_t, Vec4, const char*);
+typedef void (^IntPtrBlock)(int32_t*);
+typedef void (^ResultBlock)(int32_t);
 
 // Wrapper around a block, so that our Dart code can test creating and invoking
 // blocks in Objective C code.
@@ -80,5 +82,7 @@ typedef void (^NoTrampolineListenerBlock)(int32_t, Vec4, const char*);
 + (IntBlock)newBlock:(BlockBlock)block withMult:(int)mult NS_RETURNS_RETAINED;
 + (BlockBlock)newBlockBlock:(int)mult NS_RETURNS_RETAINED;
 - (void)invokeAndReleaseListenerOnNewThread;
-- (void)invokeAndReleaseListener:(id)_;
+- (void)invokeAndReleaseListener:(_Nullable id)_;
++ (void)blockingBlockTest:(IntPtrBlock)blockingBlock
+              resultBlock:(ResultBlock)resultBlock;
 @end
diff --git a/pkgs/ffigen/test/native_objc_test/block_test.m b/pkgs/ffigen/test/native_objc_test/block_test.m
@@ -197,4 +197,13 @@ - (void)invokeAndReleaseListener:(id)_ {
   myListener = nil;
 }
 
++ (void)blockingBlockTest:(IntPtrBlock)blockingBlock
+              resultBlock:(ResultBlock)resultBlock {
+  [[[NSThread alloc] initWithBlock:^void() {
+    int32_t result;
+    blockingBlock(&result);
+    resultBlock(result);
+  }] start];
+}
+
 @end
diff --git a/pkgs/objective_c/CHANGELOG.md b/pkgs/objective_c/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## 4.1.0-wip
 
+- Use ffigen 16.1.0
 - Reduces the chances of duplicate symbols by adding a `DOBJC_` prefix.
 - Ensure that required symbols are available to FFI even when the final binary
   is linked with `-dead_strip`.

diff --git a/pkgs/objective_c/ffigen_c.yaml b/pkgs/objective_c/ffigen_c.yaml
@@ -32,12 +32,16 @@ functions:
       - 'DOBJC_disposeObjCBlockWithClosure'
       - 'DOBJC_newFinalizableBool'
       - 'DOBJC_newFinalizableHandle'
+      - 'DOBJC_awaitWaiter'
   rename:
     'DOBJC_disposeObjCBlockWithClosure': 'disposeObjCBlockWithClosure'
     'DOBJC_isValidBlock': 'isValidBlock'
     'DOBJC_newFinalizableHandle': 'newFinalizableHandle'
     'DOBJC_deleteFinalizableHandle': 'deleteFinalizableHandle'
     'DOBJC_newFinalizableBool': 'newFinalizableBool'
+    'DOBJC_newWaiter': 'newWaiter'
+    'DOBJC_signalWaiter': 'signalWaiter'
+    'DOBJC_awaitWaiter': 'awaitWaiter'
     'sel_registerName': 'registerName'
     'sel_getName': 'getName'
     'objc_getClass': 'getClass'

diff --git a/pkgs/objective_c/lib/objective_c.dart b/pkgs/objective_c/lib/objective_c.dart
@@ -10,7 +10,8 @@ export 'src/c_bindings_generated.dart'
         ObjCSelector,
         blockRetain,
         objectRelease,
-        objectRetain;
+        objectRetain,
+        signalWaiter;
 export 'src/internal.dart'
     hide
         ObjCBlockBase,

diff --git a/pkgs/objective_c/lib/src/c_bindings_generated.dart b/pkgs/objective_c/lib/src/c_bindings_generated.dart
@@ -68,6 +68,12 @@ external ffi.Array<ffi.Pointer<ffi.Void>> NSConcreteMallocBlock;
 @ffi.Native<ffi.Array<ffi.Pointer<ffi.Void>>>(symbol: "_NSConcreteStackBlock")
 external ffi.Array<ffi.Pointer<ffi.Void>> NSConcreteStackBlock;
 
+@ffi.Native<ffi.Void Function(ffi.Pointer<ffi.Void>)>(
+    symbol: "DOBJC_awaitWaiter")
+external void awaitWaiter(
+  ffi.Pointer<ffi.Void> waiter,
+);
+
 @ffi.Native<ffi.Pointer<ObjCObject> Function(ffi.Pointer<ObjCObject>)>(
     symbol: "objc_retainBlock", isLeaf: true)
 external ffi.Pointer<ObjCObject> blockRetain(
@@ -167,6 +173,10 @@ external Dart_FinalizableHandle newFinalizableHandle(
   ffi.Pointer<ObjCObject> object,
 );
 
+@ffi.Native<ffi.Pointer<ffi.Void> Function()>(
+    symbol: "DOBJC_newWaiter", isLeaf: true)
+external ffi.Pointer<ffi.Void> newWaiter();
+
 @ffi.Native<ffi.Pointer<ObjCObject> Function(ffi.Pointer<ObjCObject>)>(
     symbol: "objc_autorelease", isLeaf: true)
 external ffi.Pointer<ObjCObject> objectAutorelease(
@@ -191,6 +201,12 @@ external ffi.Pointer<ObjCSelector> registerName(
   ffi.Pointer<ffi.Char> name,
 );
 
+@ffi.Native<ffi.Void Function(ffi.Pointer<ffi.Void>)>(
+    symbol: "DOBJC_signalWaiter", isLeaf: true)
+external void signalWaiter(
+  ffi.Pointer<ffi.Void> waiter,
+);
+
 typedef Dart_FinalizableHandle = ffi.Pointer<_Dart_FinalizableHandle>;
 typedef ObjCBlockDesc = _ObjCBlockDesc;
 typedef ObjCBlockImpl = _ObjCBlockImpl;